"In the disease state, [the PrP protein] undergoes a conformation change to a high beta-sheet content, and the PrPSC form of the protein can set up an auto-catalytic vicious cycle, whereby more PrPC is converted to the PrPSC," Dr. Wisniewski said.
In hoofed animals infected with chronic wasting disease, the PrPSC form of the prion protein is expressed in muscle and in saliva, and the diseases has been shown to be transmissible in experiments with primates.
Dr. Wisniewski and colleagues developed an active vaccine designed to protect against prion infections from an exogenous source. They used attenuated Salmonella vaccine strains that were made to express single or multiple repeats of the intact mouse PrP, or fragments corresponding to amino acids 112 to 214 of the PrP molecule, with either unaltered or tailor-made modifications of the sequences.
"We did this in such as way that normal, wild-type animals, non-genetically manipulated animals, would be amenable to this approach," he said. "This approach is particularly aimed at prionoses that are infectious in nature such as chronic wasting disease, new variant CJD, et cetera."